Plural-coil electric heater.



No. 838,884 PATENTED DEC. 18, 1906. J. F. McELROY.

PLURAL COIL ELECTRIC HEATER.

APPLICATION FILED APB-9.1906.

THE NORRIS PETERS cu. WASHINGTON, 04 c.

UNITED STATES PATENT OFFICE.

I JAMES F. McELROY, OF ALBANY, NFNV YORK, ASSIGNOR TO CONSOLI- DATED OAR HEATING COMPANY, OF ALBANY, NEW YORK, A (JOR- PORATION .OF WEST VIRGINIA.

PLURAL-COIL ELECTRIC HEATER.-

Specification of'Letters Patent.

Patented Dec. 18, 1906.

Application filed April 9, 1906' Serial No. 310.683-

To all whom, it may concern:

Be it known that I, J AMES F. MoELRoY, a citizen of the United States, residing at Albany, in the county of Albany and State of New York, have invented certain new and useful Improvements in Plural-Coil Electric Heaters, of which the following specification and accompanying drawings illustrate the invention in a form which I now regard as the best out of .the various forms in which it may be embodied.

This inventionrelates to electric he aters generallysuch, for example, as air-heaters for railway-cars and other apartmentscom posed of an insulating-support on which are mounted a plurality of resistance elements exposed to the air and adapted to be connected with different heating-circuits, so that one or more elements can be put in operation as occasion requires. It is desirable in such heaters to dispose the resistance elements so that each element will occupy a space on the support proportional to the heating intensity of that element, and in my prior patent, No. 7 35,798, I have shown such a heater with two coils of different heating intensities placed end to endthat is, occupying distinct longitudinal zones on a central core. That brings out two of the end wires of the coils at an intermediate point in the length of the heater, whereas it is desirable in many cases to have both wire terminals of a coil come out at the same end of the heater. Moreover, the end-to-end coils, when only one is in use at a time, will heat the porcelain core locally and give undesirable expansion effects.

In my present invention I improve prior electrical heaters by mounting two or more resistance elements within coextensive longi tudinal spaces side by side on the insulatingsupport. This may be done, as illustrated in the annexed drawings, by winding two or more coils parallel with each other, like a compound or plural screw-thread, about a central core that is occupying the same longitudinal zone of its surface and forming the core with corresponding compound or plural grooves to receive said coils. I also prefer to carry the end wire of each coil back through a passage in the insulating-core, according to my prior patent, No. 744,974, but arrange the passages for the return-wires and the passage for the supporting-rod in a new relation conformmg to the novel coil arrangement.

Of the accompanying drawings, Figure 1 represents a longitudinal section with the core end piece. Fig. 6 represents a perspective view of the core and coils of a shorter heater than the one in Fig. 1.

The same reference characters represent the same parts in all the views.

In the drawings, 10 is a porcelain core molded with two parallel circumferential hel lcal grooves 11 11, winding about the core like a compound screw-thread, and thus occupying the same longitudinal space. In these grooves are laid the heating-coils 12 12, each being a helically-composed coil, as known in l the art, the two coils being of equal length. These coils may either be of the same heating intensity or of different heating intensities; but in either event the core is heated uniformly throughout its length whether one or both coils are in operation.

At the end of the heater where the coils start is an insulating end piece 13, separated from the end of the core by an insulatingwasher 14 and formed with four holes 15 16, equally spaced apart in a circle, the holes 15 being adapted to receive the return-wires and having their inlets nearer together than their outlets. The core 10 is perforated with a central hole or passage 17 of square section for receiving a square rod 18, which supports the core and binds together the heater, and the core is also perforated on opposite sides of the central passage with two smaller passages 19 for receiving the return-wires. 20 is the insulating end piece at the remote end of the heater, having recesses 21 to accommodate the bends in the return-wires, and 22 is an insulatingwasher between said end piece and the end of the core.

The above construction enables the returnwires 23 of the two coils to be carried back inside of the core 10 and brought out through the apertures 15 at the same end of the heater where the coils started. The starting terminals 24 of the coils are brought out through the holes 16 in the end piece 13, and each coil ,thus has its two terminals separated by a wide distance; but all the terminals are symmetrical and conveniently reached for making outside connections.

Various changes may be made within the scope of the invention. For example, while I prefer to use helically-composed Wire-resistance elements which are laid helically around a central core the advantages of such a construction may be realized in a greater or less degree with other kinds of resistance elements mounted side by side within the same or coextensive longitudinal spaces upon an insulating-support and having means for connecting the separate elements with different external circuits.

What I claim as new, and desire to secure by Letters Patent, is

1. An electric heater comprising an insulating-support, and a plurality of resistance elements mounted side by side on said suport within coextensive longitudinal spaces, said elements having means for their respective connection With a plurality of heatingcircuits so that one or more elements may be operative.

2. An electric heater comprisin an insulating-support, and a plurality of ongitudinally-coextensive parallel tortuous resistance elements mounted on said support, each of said elements having free terminals adapting it to be individually included in a heating circuit.

grooves occupying coextensive longitudinal spaces, and reslstance-wires laid in sa1d grooves, said wires having individual external connections for a plurality of heating-circuits.

' 4. An electric heater comprising a central core, and a plurality of parallel resistancewires wound as a pluralscrew-thread about said core, said wires having terminals in number suificient to connect the different wires in different heating-circuits.

5. An electric heater comprising a core formed with plural longitudmally-coextensive helical grooves, and a plurality of electrically-distinct helically-composed resistance-wires wound about the core in said grooves.

6. An electric heater comprising a supporting-core in combination with a plurality of parallel resistance-Wires Wound like a plural screw-thread about said core, each of said coils having its two terminals carried to one end of the heater for connection with a heating-circuit and each coil having a return-wire for one of its terminals carried through the interior of the core.

7. An insulating-core for electric heaters having two parallel helical grooves occupying the same zone of its circumference, for receiving two heating-coils, said core being perforated'with a substantially central passage for receiving a supporting-rod, and with two passages on opposite sides of said central pa slsage for containing the return-Wires of the 001 s.

In testimony whereof I have hereunto set my hand, in the presence of two subscribing witnesses, the 6th day of April, 1906.

JAMES F. MOELROY.

Witnesses BEULAH CABLE, ERNEsT D. JANSEN. 

